Many couplings currently exist, making it possible to connect tubes, either to one another or to certain specific devices. Most of these couplings are conventional threaded couplings.
However, couplings which operate without a screw thread are also known.
For example, French Patent FR 2,391,411 proposes a coupling for two tubes, at least one of which is a corrugated tube including helical ribs. This coupling comprises an annular coupling element engaged in a groove of the corrugations of a first tube close to its end, so that it projects radially around the tube, and an annular stop mounted on the second tube. The annular coupling element is fastened to the stop so as to hold the two tubular elements together. In order to be sealed, this type of coupling has to be tightened a great deal, and any relative rotational movement of one tube with respect to the other would break the seal of the coupling.
Described in European Patent EP 0,444,857 B1 is a coupling making it possible to join a corrugated tube to a coupling member in a sealed manner and without a screw thread. This member comprises a cylindrical cavity in which one end of the corrugated tube is housed. A split ring which can expand radially is fastened to the end of the corrugated tube. When the tube is introduced into the cavity, the split ring is compressed and locks into a circumferential groove made in the cylindrical cavity. Sealing is provided by one or more toric seals mounted on the corrugated tube behind the split ring. One of the main disadvantages of this type of coupling is that it is almost impossible to take apart without destroying it.